This invention relates to an improved method for preparing sphere-based retroreflective sheeting.
Retroreflective sheeting is commonly used for safety or advertising purposes, and generally wherever it is desired to draw attention to a surface when light impinges upon the surface from the direction of the viewer. One form of retroreflective sheeting material having high brilliance incorporates glass beads or spheres which provide a lens action in conjunction with a reflective material behind the spheres, such as a metallized surface or film. Since retroflective sheeting of this type is most often used in outdoor locations, sheeting has been developed in which the glass spheres and reflective surface behind the spheres is enclosed between weather-resistant plastic films or sheeting.
U.S. Pat. No. 3,190,178 to McKenzie discloses improvements in sphere-based, closed lens type retroreflective sheeting, especially means for anchoring the sphere lens elements between cover and backing films to provide a hermetic seal against moisture penetration under varying conditions of outdoor use. Although high brilliance is obtained by the sheeting of the McKenzie patent, by maintaining air pockets between the transparent cover film and the surfaces of the spheres which are not coated with a reflecting metallic deposit, the structure still suffers from delamination due to inadequate bonding.